I got a small sofa from an Opshop 2 months ago. I checked it well and it was nice clean and sturdy. Just that when I took all the covers off to wash them at home , I found long painted finger nails in foam :( But I haven't made an opinion and things like these can happen when it is second hand stuff . The concept of Op shop is new for me because I didn't have it where I come from.

Definitely not undies or socks, but otherwise I don't think I'd be worried. I would assess each item on its own merits but I love shopping in op shops and many of my best clothes and my most elegant shoes were bought there.

Undies, and I would be wary about buying electrical goods. Having said that, I have scored some great designer clothes bargains from a new op shop which has just opened in a fairly affluent part of Brisbane. I also bought a couple of decidedly quirky handbags from the same shop. All of the purchases at great prices too!

I would not want secondhand underwear or swimwear. I have bought baby socks at an op shop and used them when my dog had a sore foot. I try not to buy anything new or secondhand that has a high synthetic content.
I think it is Environmentally responsible to shop at op shops. Often the secondhand goods look almost new. Some people are very wasteful and justify buying new things when others are still good and feel good about themselves by donating them. Lately I have heard that opshops need to dump ladies wear in particular as they get more than they can carry. I wish people would just buy less. Synthetics clothes are as bad as plastic on the environment, so I try not to buy them either new or secondhand, although it is hard to find clothes with no synthetic content.